import javax.media.j3d.*;
import javax.vecmath.*;

public class RevolvingUniverse extends Object
{
  VirtualUniverse universe;
  Locale locale;
  BranchGroup viewPlatformRoot;
  TransformGroup viewPlatformTransform;
  ViewPlatform viewPlatform;
  View view;
  Canvas3D canvas;
  float zViewDistance;

  public RevolvingUniverse(Canvas3D drawingCanvas, float zViewDist)
  {
    canvas = drawingCanvas;
    zViewDistance = zViewDist;
    universe = new VirtualUniverse();
    locale = new Locale(universe);
    viewPlatformRoot = new BranchGroup();
    
    viewPlatformTransform = new TransformGroup();
    viewPlatformTransform.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
    viewPlatformTransform.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
    
    setupView(drawingCanvas);
    setupViewPlatform();

    view.attachViewPlatform(viewPlatform);
    locale.addBranchGraph(viewPlatformRoot);
  }

  private void setupView(Canvas3D drawingCanvas)
  {
    view = new View();
    view.addCanvas3D(drawingCanvas);
    view.setPhysicalBody(new PhysicalBody());
    view.setPhysicalEnvironment(new PhysicalEnvironment());
  }

  private void setupViewPlatform()
  // Translate the view platform back by zViewDistance metres
  {
    viewPlatform = new ViewPlatform();
    setViewingDistance(zViewDistance);

    Alpha alphaX = new Alpha(-1,10000);
    Alpha alphaY = new Alpha(-1,31415);
    BoundingSphere lifeUniverseEverything = new BoundingSphere();
        
    TransformGroup viewPlatformTransformRotX = new TransformGroup();
    viewPlatformTransformRotX.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
    viewPlatformTransformRotX.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);

    RotationInterpolator interpolatorRotX =
       new RotationInterpolator(alphaX,viewPlatformTransformRotX);  
    interpolatorRotX.setSchedulingBounds(lifeUniverseEverything);
    // Since the rotation will be about the local Y axis by default
    // we need to rotate the axis by -PI/2 about Z to obtain an X rotation
    Transform3D zRotate3PIby2 = new Transform3D(new Matrix4d( 0 , 1 , 0 , 0 ,
                                                             -1 , 0 , 0 , 0 ,
                                                              0 , 0 , 1 , 0 ,
                                                              0 , 0 , 0 , 1 ));
    interpolatorRotX.setTransformAxis(zRotate3PIby2);
    viewPlatformRoot.addChild(interpolatorRotX);

    TransformGroup viewPlatformTransformRotY = new TransformGroup();
    viewPlatformTransformRotY.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
    viewPlatformTransformRotY.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);  
    
    RotationInterpolator interpolatorRotY =
       new RotationInterpolator(alphaY,viewPlatformTransformRotY);  
    interpolatorRotY.setSchedulingBounds(lifeUniverseEverything);
    // Note that the rotation is about the local Y axis by default
    viewPlatformRoot.addChild(interpolatorRotY);

    viewPlatformTransform.addChild(viewPlatform);
    viewPlatformTransformRotY.addChild(viewPlatformTransform);    
    viewPlatformTransformRotX.addChild(viewPlatformTransformRotY);
    viewPlatformRoot.addChild(viewPlatformTransformRotX);
  }

  public void setViewingDistance(float viewDistance)
  {
    zViewDistance = viewDistance;
    Transform3D transform = new Transform3D();
    transform.set(new Vector3f(0.0f, 0.0f, zViewDistance));
    viewPlatformTransform.setTransform(transform);
  }

  public View getView()
  {
    return view;
  }

  public TransformGroup getViewPlatformTransform()
  {
    return viewPlatformTransform;
  }

  public void addBranchGraph(BranchGroup bg)
  {
    locale.addBranchGraph(bg);
  }
}